The present invention relates to an electrical steering lock device for anti-theft of a vehicle and a related method.
An electrical steering lock device, disclosed in Japanese Patent Provisional Publication No. 2002-205622, is arranged to render a lock shaft, adapted to protrude and retract in linkage with an electric motor, engageable with and disengageable from a steering shaft to lock and unlock rotation of the steering shaft.
FIGS. 1 and 2 show how a steering shaft 101 is unlocked from a locked condition to an unlocked condition in an electrical steering lock device 100 of the type mentioned above. Under such a locked condition of the steering shaft 101 as shown in FIG. 1, a wall surface of a lock groove 103 is held in strongly pressured contact with the lock shaft 102 due to a restoring force X applied to the steering shaft 101 resulting from frictional resistance between tires and road surface. For this reason, during a process in which the steering shaft 101 is unlocked, the lock shaft 102 is applied with increased load when the lock shaft 102 is moved from the lock groove 103 (in a way as shown in FIG. 1→FIG. 2), whereas no load is applied to the lock shaft 102 after the lock shaft 102 has disengaged from the lock groove 103 (in a way as shown in FIG. 2→FIG. 3).
As a result, the lock shaft 102, which protrudes and retracts upon receipt of a fixed drive force from the electric motor, undergoes an issue with an inability of disengaging from the lock groove 103 depending upon a magnitude of load being applied.